The present invention relates to phosphorus-containing halogenated unsaturated polyester compositions, manufactured from halogenated unsaturated polyesters derived from epihalohydrins.
Synthetic materials derived from unsaturated polyesters are well known to those skilled in the art. By virtue of their good mechanical properties combined with a relatively low density, there are large markets for these products in civil, aeronautical and naval engineering, these being fields where the demand for fire-resistant materials is increasing. Now, synthetic materials derived from conventional polyesters possess the major disadvantage of being inflammable and of burning readily. It has thus proved to be absolutely necessary to improve the fire-resistance of these products.
For this purpose, it has already been proposed to incorporate into them inert and unreactive flameproofing additives such as antimony oxide, chlorinated paraffins or triphenylstilbene. This technique can provide only very temporary flameproofing and leads, furthermore, to the production of heterogeneous and opaque products, the mechanical properties of which are less good.
Another known technique, which is markedly more valuable because it leads to permanent flameproofing, consists of incorporating chemically into the polyester chain as it is being formed, a difunctional flameproofing substance, for example a halogenated substance such as chlorendic acid, tetrachlorophthalic acid or anhydride, or a chlorinated polyol or its corresponding epoxy derivative. Chlorinated organic acids and anhydrides, such as chlorendic acid, are unfortunately expensive and lead, furthermore, to the production of polymers which offer little resistance to chemical agents and to the effect of light, and this greatly limits their field of application.
The use of epichlorohydrin, a readily available starting material which is much less expensive, as the flameproofing substance, was claimed in French Pat. No. 1,167,220 of 25/2/1957 in the name of Solvay & Cie. The manufacture of halogenated polyesters by non-catalytic copolymerization of epichlorohydrin and maleic anhydride is described in this patent.
In Luxembourg Patent application No. 66,454 of 10/11/1972, corresponding to copending U.S. Application Ser. No. 401,806, filed on Sept. 28th, 1973, there is, furthermore, described "super-halogenated" unsaturated polyesters, that is to say polyesters which possess a halogen content higher than that of the monomers incorporated into the polyester chain, and which are also derived from an epihalohydrin. These super-halogenated unsaturated polyesters are prepared by copolymerization of maleic anhydride, used individually or as a mixture with another organic anhydride, and at least one .alpha.-epihalohydrin, in the presence of a titanium tetrahalide, the halogen being taken from the group consisting of chlorine and bromine.
The flameproof crosslinked polyester resins manufactured by employing these halogenated unsaturated polyesters derived from epihalohydrins combine good mechanical properties, comparable to those of the polymers manufactured by crosslinking conventional polyester resins, with resistance to chemical agents which is excellent compared to commercial compositions reputed to be flameproof. Their flame-resistance properties could however be improved.